Effect of short- and long-lasting chilling on pre-rRNA synthesis and transport in root meristematic cells of three soybean cultivars

Abstract

Autoradiographic studies of ³H-uridine incorporation (20-min incubation) and dynamics of radioactive particle translocation from nucleolus into cytoplasm (following 80-min postincubation in non-radioactive medium) in root meristematic cells of soybean have been carried out. The experiment was performed with plants subjected to 4-day acclimation in chilling or subjected to 2-hour cold stress and control plants. Three cultivars of soybean: Mazowia, Polan and Progres (cultivated in Poland) were used in the experiment.

It has been shown that in control conditions the greatest number of RNA precursor is incorporated into nucleoli after 20-min incubation. Following 80-min postincubation cytoplasm is the most radioactive area of the cell - this mainly testifies to dynamic translocation of radioactive ribosome subunits from nucleolus into cytoplasm.

In chilling conditions the reduction of ³H-uridine incorporation into cells occurs, as compared to control conditions. Plants subjected to a 4-day acclimation incorporate the radioactive precursor more intensively than plants subjected to cold stress.

Following 80-min postincubation - in the case of acclimated plants - the nucleolus is the most radioactive area of the cell, which testifies to accumulation of pre-rRNA in it. After the cold stress cytoplasm is more radioactive than the nucleolus. In all three cultivars the processes of synthesis and transport of pre-rRNA particles are similar, only their intensity is different.

Morphometric measurements of nucleoli in all cultivars subjected to 4-day chilling have shown that root cell nucleoli are larger than those in control. This phenomenon can be connected with stronger inhibition of rRNA transport than its synthesis.